Apparatus for coating



1959 L. HORVNBOSTEVL 2, 7

APPARATUS FOR COATING Filed Jan. 28, 1957 hZ En far no w flown/1905 754United States Patent APPARATUS FOR COATING Lloyd Hornbostel, Beloit,Wis., assiguor to Beloit Iron The instant invention relates toapparatus; for coating a sheet or the like, and more particularly, toapparatus for applying a uniform coating to a travelling sheet such as apaper web. 7

Ordinarily, in the coating of a travelling sheet or web fabric, plasticfilm, paper or the like, the sheet is backed by a supporting surface andthe coating. is applied to the exposed side thereof using a doctor tosmooth the coat ing material on the sheet andinsure uniform applicationthereof. Althoughthe instant invention may have use in the coating ofany of such sheets, it is particularly useful in the coating of paperwebs and will be described primarily with respect to this use.

In coating devices of this general type the advantages of small(diameter) doctor rolls are well known in the art. The main backing rollor platen rollis ordinarly of substantial size and its structure andinternal supports blades have been used because these can be adequatelysupported, but such blades lack a number of advantages which the doctorroll provides, including particularly the advantage ofbeing able torotate the doctor roll. Loading of the doctor rolls has been attemptedby the use of other rolls, but'the difficulties also increase greatlywith increases in the width of'the. machine.

The instant invention offers a solution to the problems involved in theuse of a relatively small flexible doctor roll with the usual relativelyrigid large platen roll. In

the instant invention loading of the doctor roll is accom-.

plished by the use of one or more members presenting a resilient surfaceslidably engaging the back side of the doctor roll and by .the use offluid pressure means operating against the back side of the resilientsurface for the full length of the doctor roll so as to uniformly loadthe doctorroll against the platen roll throughout the length ing to thesheet, a member presenting a resilient surface slidably engaging saiddoctor roll, and fluid pressure means urging said resilient surfaceagainstthe doctor 'ice - 2 inequalities of the platen roll due to heatas well as variations in the sheet itself.

It is, therefore, an important object of the instant invention toprovide an improved apparatus for coating travelling sheet'material orthe like.

It is a further object of the instant invention to provide an improvedapparatus for coating a travelling sheet, comprising a relatively rigidplaten roll supporting the travelling sheet wrapped thereby, arelatively flexible doctor roll defining with said platen roll a nipthrough which the sheet passes, coating means at the on-coming side ofthe nip and on the doctor roll side of the sheet applying coatroll toload the doctor roll against said platen roll.

Other and further objects, features and advantages of the presentinvention will become apparent to those skilled in the art from thefollowing detailed disclosure thereof and the drawings attached heretoand made a part hereof.

On the drawings:

Figure l is an elevational view, with parts shown in section and partsshown diagrammatically, of a coating apparatus embodying the instantinvention;

' Figure 2 is a fragmentary top plan view showing essentiallydiagrammatically an oscillating drive for one end of the doctor rollshown in Figure 1; and

Figure 3 is a fragmentary elevational view, with parts shown in sectionand parts shown diagrammatically showing another embodiment of theinstant invention.

As shown on the drawings:

In Figure 1 there is shown a coating apparatus indicated generally bythe reference numeral 10 embodying the instant invention. The apparatus10 comprises a relatively rigid large platen roll 11 supporting atraveling sheet or paper web W wrapped thereby. The web W travels in.the direction indicated by the arrow from beneath the platen roll 11along the uprunning side thereof. The platen roll 11 is rotated by drivemeans D (shown diagrammatically) of .the usual type which include asuitable motor and speed control gearing assembly, which need not befurther described herein. The platen roll 11 is of substantial diameterd and is provided with suitable internal supports so that it is rigid(which respect to the members of lesser size which will be describedhere- I inafter); and, the platen roll 11 is provided with a smoothsurface. Also, means (not shown) for supplying is wrapped about theplaten roll 11.

The. apparatus 10 is also provided with a relatively flexible doctorroll 12 defining a nip N with'the platen thereof. The resilient means,maybe in the form of.a n

elastorner tubular member which receives the fluid pre ssure within thetube "and which engages the back side of the doctor roll so as'tofunction as a wiper therefor. Such tubular members apply pressureuniformly throughout the full length of the doctor roll so that no'crowning isnecessary and a coating of uniform thickness is maintained bythe doctorrollacross the'entire width of the coated.

sheet backed by 'the'platen' roll. 'In addition, the resilientsurfacejof' the tubular member slidably engaging the doctor rollfpermitsrotation thereof in either direction as well as oscillating movementthereof longitudinally of the axisofthe doctor roll. [Theuniformapplicationof fluid pressure (via the resilient member) throughout thefull n h: p h doctor a l a P rm s emana e a roll 11 along theuprunningside thereof." .The web W passes through the nip N whereat thedoctor roll-12 levelsthey coating on the exposed side of theweb W sothat a uniformvapplication of coating material is obtained.

.At the on-comingisidelof the nip-N, or beneath the nip N, coating meansin the form of a coating roll. 13 applies a coating material M to theexposed side of the web WP As here shown the coating roll 13 is mountedin a tankai 14 which contains a bath of the coating material Thecoating: roll 13 may be provided with drive means (not shown).

partially submerging the coating roll 13:

ifdesired or it may'be rotated by frictional engagement with theweb Wbacked by the 'platen. roll 11, ashere shown. As the coatingroll 13rotatesit p'icks up-coating material M from the tank 14 and applies thesame to the material M so that a uniform application thereof isaccomplished. The doctor roll 12 is rotated by means of drive means D(shown diagrammatically) which again mcludes the usual motor and speedand direction control gearing well understood in the art. Preferably,the doctor roll 12 is rotated as shown by the arrow in a directionopposite to the rotation of the platenroll 11 so as to obtain the mosteffective smoothing of the coating material M and the most uniformdistribution thereof. 'In the prior art, a coating roll such as the roll12 which is relatively small, having a diameter d that may range from asmuch as one-third of the platen roll diameter d to as little as perhapsone-twentieth thereof, is so flexible that it is difficult or impossibleto apply a uniform layer of coating material M. As previously mentioned,crowning of such a doctor roll results in a lack of uniformity in thesurface speeds along the length of the roll and various prior loadingdevices for such a doctor roll were ineffective.

In the instant invention, however, members 15 and 16 present resilientsurfaces slidably engaging the doctor roll 12 so as to effectively loadthe doctor roll 12 against the platen roll 11 in a manner which will bedescribed.

A structural frame member 19 secured to a stationary fixture such as thefloor F (but adjustable via set screws 17 and 18) presents a pair ofsemi-cylindrical mounting means 20, 21 at the back side of the'doctorroll 12 just slightly above and slightly below the doctor roll 12 formounting the resilient members 15 and 16, thereby providing a fixedbacking for the resilient members 15 and 16. By suitable adjustment ofthe position of the frame element 19 relative to the platen roll 11 theactual thickness of coating material M passing through the nip N on theweb W may be controlled. 7

As here shown, the resilient members 15 and 16 are tubes of elastomericmaterial, such as rubber, synthetic rubbers, polyethylene,polytetrafluoroethylene (Teflon), and the like resilient plasticmaterials. The preferred material here used is polytetrafluoroethylene.The members 15 and 16 are tubes sealed at the ends which com municatewith a source of fluid under pressure, here indicated diagrammaticallyat S. A pump P maintains air pressure in the source tank S and valves 22and 23, re spectively, control the flow of air into the interior of thetubes 15 and 16. As will be appreciated, the tubes 15 and 16 extend thefull length of the doctor roll 12, so that the fluid pressure uniformlydistributed within the tubes 15 and 16 is in turn uniformly imparted tothe doctor roll 12 and the doctor roll 12 is in turn uniformly urgedthroughout its length against the platen roll 11.

As will be appreciated, the resilient members 15 and 16 are preferredbecause these members actually contact the doctor roll 12 along aminimum of surface area. The members 15 and 16 slidingly engage thedoctor roll 12 so as to permit rotation thereof. The loading forceapplied by the members 15 and 16 is applied generally along a lineconnecting the diameter of the doctor roll 12 and the' center of theparticular tube 15 or 16 because of the sliding engagement between theelements 12, 15 and 16. This sliding engagement also effectively permitswiping of the surface of the doctor roll by the tubes 15 and 16. As willbe seen, a drip pan 24 is provided to receive coating material M wipedoff the doctor roll 12 by the lower tube 16. Any material wiped off bythe upper tube 15 can flow down past the lower tube 16 throughpassageway 25 into the drip pan 24.

The tubes 15 and 16 afford the additional advantage that they are loadedagainst the doctor roll 12 so as to effectively wipe the same clean. Thetubes 15 and 16 also afford the advantage that, while loaded against thedoctor roll 12, they effectively permit limited oscillating or axialmovement of the roll 12. Oscillating movement of the roll 12 isimportant to compensate for any minor inequalities in the operation ofthe platen roll 11 as well as for smoothing out possible wrinklesin theweb W.

Referring to Figure 2, it will be noted that a fragmentary top view ofone side of the device 10 is shown, showing the top side of the web Wpassing on up over the platen roll 11. The doctor roll 12 is shownrotatably mounted at one end in bearings 26 (shown diagrammatically).The top resilient tube 15 retained in the backing element 20 is shownurged against the back upper portion of the rotating doctor roll 12. Thedoctor roll 12 is mounted in the bearings 26 for limited axialoscillation. Such axial oscillation pan be effected by the use of any ofa number of driving" means, but here shown is an arm 27 mounted on afixed pivot 28 for limited pivotal movement toward and away from theroll 12 and against the rotating roll journal 120, so as to oscillatethe roll 12 axially. The pivot arm 27 is moved by a pneumatic piston andcylinder (shown diagrammatically at 29) mounted on a fixed pivot 30 andconnected to the middle of the pivot arm 27 by a pivot pin 31. Theactuation of pneumatic piston'and cylinder assemblies such as theassembly 29 is well understood by those skilled in the art and need notbe further described herein in detail; but it should be mentioned thatconsiderable force can be applied to the pivot arm 27 and a slowoscillating movement may be thus accomplished in the operation of theinstant device.

Referring now to Figure 3, it will be seen that a somewhat ditferentarrangement indicated generally by the reference numeral is shown forthe application of a coating material M-l at a nip N-1 formed between aplaten roll 111 and a rotating doctor roll 112. The platen ro-ll 111 iscovered by a web W-l which passes through the nip N-l. A pair ofresilient tubes 115, 116 having substantially the same structure as thetubes 15 and 16 of Figure 1 are loaded with compressed air andresiliently urge the doctor roll 112 against the platen roll 111 in themanner already described. The tubes 115, 116 are backed bysemi-cylindrical rigid backing members 120, 121, respectively which aremounted in a fixed frame 119. The frame 119 also mounts walls 132 and133 which form a V-shaped receptacle for the coating bath M-l. The wall133 is spaced slightly from the wall 132 at the bottom thereof to form agate for flowing controlled amounts of the material M-l just over thetop of the top resilient tube and onto the top of the doctor roll 112.The doctor roll 112 turns upwardly at the nip N-l and against the flowof coating material M-l (although permitting the desired limited amountof flow of material onto the web W-l), while the'web W-l is drawndownwardly at the nip N-l by the platen roll 111. The advantage here isthat the wiping effect of the roll 112 on the resilient tube 115 is suchthat coating material is constantly retained at the base of the walls132, 133 and the only coating material escaping therefrom is thatapplied in the desired amount to the surface of the web W-l. The coatingwiped from the surface of the roll 112 is retained precisely in theposition desired for additional coating to be applied to 1. Apparatusfor coating a travelling sheet, compris-' ing a relatively rigid platenroll supporting the travelling sheet wrapped thereby, a relativelyflexible doctor roll defining with said platen roll a nip through whichthe sheet passes, coating means at the on-coming side of the nip and onthe doctor roll side of the sheet applying jcoating to the sheet, aplurality of members each presenting a separate resilient surfaceslidably engaging said doctor roll, and fluid pressure means urging eachsaid resilient surface against the doctor roll to load the doctor rollagainst said platen roll.

2. Apparatus for coating a travelling sheet, comprising a relativelyrigid platen roll supporting the travelling sheet wrapped thereby, firstdrive means rotating said platen roll, a relatively flexible doctor rolldefining with said platen roll a nip through which the sheet passes,coating means at the on-coming side of the nip and on the doctor rollside of the sheet applying coating to the sheet, a plurality of memberseach presenting a separate resilient surface slidably engaging saiddoctor roll, and fluid pressure means urging each said resilient surfaceagainst the doctor roll to load the doctor roll against said platenroll.

3. Apparatus for coating a travelling sheet, comprising a relativelyrigid platen roll supporting the travelling sheet wrapped thereby, firstdrive means rotating said ,platen roll, a relatively flexible doctorroll defining with said platen roll a nip through which the sheetpasses, second drive means rotating said doctor roll, coating means atthe on-coming side of the nip and on the doctor roll side of the sheetapplying coating to the sheet, a plurality of members each presenting aseparate resilient surface slidably engaging said doctor roll, and fluidpressure means urging each said resilient surface against the doctorroll to load the doctor roll against said platen roll.

4. Apparatus for coating a travelling sheet, comprising a relativelyrigid platen roll supporting the travelling sheet wrapped thereby, arelatively flexible doctor roll defining with said platen roll a nipthrough which the sheet passes, drive means rotating said doctor roll,coating means at the oncoming side of the nip and on the doctor rollside of the sheet applying coating to the sheet, a plurality of memberseach presenting a separate resilient surface slidably engaging saiddoctor roll, and fluid pressure means urging each said resilient surfaceagainst the doctor roll to load the doctor roll against said platenroll.

5. Apparatus for coating a travelling sheet, comprising a relativelyrigid platen roll supporting the travelling sheet wrapped thereby, arelatively flexible doctor roll defining with said platen roll a nipthrough which the sheet passes, means oscillating said doctor rolllongitudinally of its axis, coating means at the on-coming side of thenip and on the doctor roll side of the sheet applying coating to thesheet, a pair of members each presenting a separate resilient surfaceslidably engaging said doctor roll, and fluid pressure means urging eachsaid resilient surface against the doctor roll to load the doc tor rollagainst said platen roll.

6. Apparatus for coating a travelling sheet, comprising a relativelyrigid platen roll supporting the travelling sheet wrapped thereby, arelatively flexible doctor roll defining with said platen roll a nipthrough which the sheet passes, drive means rotating said doctor roll,means oscillating said doctor roll longitudinally of its axis, coatingmeans at the on-coming side of the nip and on the doctor roll side ofthe sheet applying coating to the sheet, a pair of members eachpresenting a separate resilient surface slidably engaging said doctorroll, and fluid pressure means urging each said resilient surfaceagainst the doctor roll to load the doctor roll against said platenroll.

7. Apparatus for coating a travelling sheet, comprising a relativelyrigid platen roll supporting the travelling sheet wrapped thereby, 'arelatively flexible doctor roll defining with said platen roll a nipthrough which the sheet passes, coating means at the oncoming side ofthe nip and on the doctor roll side of the sheet applying coating to thesheet, a pair of expandable resilient members each slidably engagingsaid doctor roll along the full length thereof, and a source of fluidunder pressure expanding each said member to urge the doctor rollagainst the platen roll uniformly along the full length of the doctorroll.

8. Apparatus for coating a travelling sheet, comprising a relativelyrigid platen roll supporting the travelling sheet wrapped thereby, arelatively flexible doctor roll defining with said platen roll a nipthrough which the sheet passes, coating means at the on-coming side ofthe nip and on the doctor roll side of the sheet applying coating to thesheet, a plurality of elastomer tubular members each slidably engagingsaid doctor roll along the full length thereof, and means expanding eachmemher to urge the doctor roll against the platen roll uniformly alongthe full length of the doctor roll.

References Citedin the file of this patent UNITED STATES PATENTS1,643,117 Gustavson Sept. 20, 1927 1,956,561 Coates May 1, 19341,956,562 Coates May 1, 1934 1,983,982 Knollenberg Dec. 11, 19341,993,055 Gerstenberg Mar. 5, 1935

